WCIPEG 2017-2018 Test

The Carol Economy is a set of people who interact and share hearts (<3) with each other. In order to be part of the Carol Economy, each person must be friends with every other person. Carol is trying to set up a larger Carol economy between some of her friends. There are $N$ people, and $K$ pairs of people know each other. Help Carol calculate the amount of new friendships that must be made.

Input Specification

The first line of input contains the integers $N$ $(1\le N\le 1000)$ and $K$ $(0\le K\le {10}^6)$.

Output Specification

Output the number of new friendships that must be made. This number is guaranteed to be non-negative.

Sample Input

10 8

Sample Output

37